The present invention relates to an actuator.
Conventionally, a type of actuator has been known that includes dielectric rubber layers (dielectric elastomer layers) and conductive rubber layers provided on the front and back faces of each dielectric rubber layer. This type of actuator is operated by executing and stopping voltage application to the conductive rubber layers so that the dielectric elastomer layers are expanded or contracted.
Such actuators are used for artificial muscles. More specific examples include an actuator disclosed in Japanese Laid-Open Patent Publication No. 2009-124875. The actuator is formed by wrapping a sheet having dielectric elastomer layers and conductive rubber layers about a coil spring, so that the sheet is rolled. Voltage application to the conductive rubber layers on the front and back faces of each dielectric elastomer layers of the sheet is executed or stopped, so that the rolled sheet is expanded or contracted along the direction of expansion and contraction of the coil spring.
The coil spring in the actuator urges the actuator along the axial direction of the rolled sheet. The actuator is urged along the axial direction thereof to minimize expansion of the actuator in directions perpendicular to the axial direction when the actuator operates to expand along the axial direction. Accordingly, the displacement (operational amount) of the actuator in the axial direction is maximized as much as possible.